Mark RenderThread::HostAllocateSharedMemoryBuffer for deprecation.

This is a change to a comment only.

Bug: 795291
Change-Id: I3665a92f2132d6c7af7441828b4f18d276bbb5cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1569217
Auto-Submit: Matthew Cary <mattcary@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652572}

content/public/renderer/render_thread.h

@@ -81,6 +81,9 @@ class CONTENT_EXPORT RenderThread : virtual public ChildThread {
   virtual void SetResourceDispatcherDelegate(
       ResourceDispatcherDelegate* delegate) = 0;
 
+  // DEPRECATED: Use mojo::Create*SharedMemoryRegion (see
+  // mojo/public/cpp/base/shared_memory_utils.h) instead.
+  //
   // Asks the host to create a block of shared memory for the renderer.
   // The shared memory allocated by the host is returned back.
   virtual std::unique_ptr<base::SharedMemory> HostAllocateSharedMemoryBuffer(